Interesting question. Mostly it's the overall image of what they like to present.
G@MES/MEGA HUNK-Ch prefers to recruit straight muscular twunks to hunks. They emphasizes on the
straight & manly men aspect, as it provides a type of fantasy for the gay audience. Their scenes are quite tame compared to some other studios.
Coat Corporation isn't much difference in the recruiting part, but they have a tendency to pick even younger models into their ranks. They also do bukkakes, orgies, kinkier stuffs, etc. although not really that hardcore, just on the surface level.
Men's Rush.TV recruits a variety of twinks, twunks & muscular guys. Straight to gays. They mix all of them up in many scenes. For this one studio they're really into the leaner body type. Their scenes are mostly tame too.
KO Company has its divided sections of muscular guys and twinks, it's like they're completely aware of their 2 different markets. Their promotional materials tend to showcase rough scenes, although they really aren't that in the final product. Back in the days they had more hardcore stuffs, like scat porn (I really don't like this genre, it traumatized me back then when I saw one
), etc. but they kinda became way tamer & more mainstream now.
ACCEED is into twinks & twunks. They also do stuffs like light bdsm, golden shower, orgies, bukkakes & stuffs.
JUSTICE Corporation stars younger models, typically twinks to twunks. They range from gay, bi to straight models with rougher scenes. The trailer of their works are so long, we can basically tell the whole video, lol. The former CEO was actually arrested when they hired & tricked a 17 years old model back in 2015, lol. But the company is still standing now.
And there are many other more like
STR8 BOYS which, as the name implies, mainly recruits straight young adults & recently got their own website;
G-BOT features both gay & straight men, their cover & promotional materials look like magazine shots, lol;
Healing Boy Movie likes their pretty twunky & muscular boys; etc. (I'm just too lazy at this point).
All of the above is just based on my personal observation. It truly is a blurry line as
there isn't necessarily a "correct" answer. Each company has their own different labels of various sub-genres & doesn't always follow the patterns that I said (i.e. HUNK-Ch would also recruit gay men of course; ACCED also recruits muscular men, etc.). Models also do come & go. Sometimes they switch companies too.
